The radii of the base of two cylindrical tins, P and Q are r and 2r respectively. If the water level in p is 10cm high, would be the height of the same quantity of water in Q?

A.

4.5cm

B.

5.0cm

C.

7.5cm

D.

20.0cm

Correct answer is A

volume of cylinder = \(\pi r^2h\)

volume of cylinder p = \(\pi r^2 \times 10\)

= 10\(\pi r^2\)

volume of cylinder Q = \(\pi (2r)^2 h\)

= 4\(\pi r^2\)h

4\(\pi r^2 = 10 \pi r^2 h\)

h = \(\frac{10}{4} = 4.5cm\)